A single tactical aircraft could not be a sufficient replacement, but it is concievable that an array, or constellation of manned, or unmanned tactical aircraft could perform in this regard.
A group of "MC2A" UAVs could even be more effective than a single, ultra-expensive, crew-filled, E-10.
For instance, it can be spread out to provide a greater range, and scope of coverage than a single aircraft.
If one or two of the group are destroyed, the rest of the group still has some functionality.
The loss of several units may be significantly less costly than a single E-10- particularly so given the loss of life involved.
Currently, the nominal mission endurance of modern AEW&C platforms is primarily limited by the physical needs and limitations of the crew. But this is a non-issue if the operators are safely located at a ground station thousands of kilometers distant from danger.
Anyway, these are some possibilities, and there are likely more that escape me at the moment.